1. Field of the Invention
The present invention relates to a film forming apparatus and a film forming method, and particularly to formation of piezoelectric film in a piezoelectric actuator used in an ink jet head or the like.
2. Description of the Related Art
A so-called aerosol deposition method (AD method) is known as a method for manufacturing a piezoelectric actuator used in an ink jet head or the like. For example, JP-A-2003-306762 discloses a method for generating aerosol by dispersing fine particles of piezoelectric material into gas in an aerosol chamber, guiding the generated aerosol to a jet nozzle in a film forming chamber by the difference in pressure between the aerosol chamber and the film forming chamber which is caused by reducing the internal pressure of the film forming chamber, thereby jetting the aerosol to the surface of a substrate. According to this method, the fine particles contained in the aerosol collide with and deposit onto the substrate, thereby forming piezoelectric film.
When a thin film is formed, it is difficult to control the thickness of the film perfectly, and particularly, there is a tendency that the variation in the film thickness becomes larger as the film forming speed is increased. Therefore, it has been adopted to control the film thickness as needed by setting an initial condition experientially, measuring the film thickness during film formation and performing parameter control to some degree.
However, as in the case of the AD method, in a case where a method for executing the film forming process in reduced pressure is adopted, and the film thickness is measured during the film formation, there must be taken an extremely complicated procedure in which the internal pressure of the film forming chamber is temporarily returned to normal pressure, a substrate placed in the film forming chamber is taken out to measure the film thickness, the substrate is returned to the inside of the film forming chamber again after the film thickness is measured, and then the internal pressure of the chamber is adjusted.